Drying,spreading and radiant heating of tubular knitted,acrylic fabrics



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Dec l N- N ON E OH A @Fm 3,543,409 DRYING, SPREADING AND RADIANT HEATING OF TUBULAR KNITTED, ACRYLIC FABRICS Joseph F. Fuhs and Samuel Z. Fain, Williamston, N.C.,

assignors to Beaunit Corporation, New York, N.Y., a

corporation of New York Filed Oct. 31, 1968, Ser. No. 772,076 Int. Cl. F26b 5/14 U.S. Cl. 34-14 2 Claims ABSTRACT F THE DISCLOSURE Dyed, tubular knitted, acrylic fabric having improved handle and being essentially free of crack marks is prepared by extracting free moisture from the dyed fabric; heating the dyed fabric at a temperature and for a time sufficient to provide a fabric surface temperature of about 20G-230 F. and a moisture content in the fabric of less than about 5 percent by weight; spreading and steam treating the dyed fabric to provide uniform moisture content on the fabric and a uniform width throughout the fabric; and then treating the dyed fabric wtih radiant heat at a temperature and for a time sufficient to obtain a fabric surface temperature of about 20G-250 F. The dyed fabric so treated will have outstanding hand or handle and an extremely low degree of crack or crease marks. The dyed, tubular knitted, acrylic fabric so treated may then be processed by conventional means into garments and the like.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to dyed, tubular knitted, acrylic fabric having an excellent handle and essentially free of crack marks or streaks and to a process for providing such improved fabric.

Description of the prior art Tubular knitted fabrics have increasingly important uses as knit wear gains popularity in modern fashion markets. Various processing steps have been proposed and used for treating tubular knitted fabrics to improve various properties, such as shrinkage, handle, appearance, and the like. Commercially, normal practice involves wet steaming the fabric, followed by drying and finish calendering. Although improvement in the appearance, handle and the like may be achieved following this procedure, processes which enable the fabric to be processed more economically with substantially improved properties are always desired. This is particularly true in the case of processing dyed, tubular knited fabric comprised of acrylic fibers. A problem exists in that dyed, tubular knitted, acrylic fabric has a tendency to develop crack or crease marks which appear as streaks in the dyed fabric. The streaky appearance of the dyed fabric may severely handicap the use of this type of fabric in conventional knit wear.

SUMMARY OF THE INVENTION It is an object of the present invention to provide dyed, tubular knitted, acrylic fabrics which have an improved handle or appearance.

It is another object of the present invention to provide dyed, tubular knitted, acrylic fabrics which are essentially free from crack or crease marks and which do not have a streaky appearance.

It is a further object of the present invention to provide a process in which a critical sequence of process steps is followed to provide the improved fabrics of this invention.

ited States Pater Other objects and advantages of the present invention will be apparent from the following detailed description of the invention.

Dyed, tubular knitted, acrylic fabric having improved handle and essentially free of crack or crease marks are prepared by:

(l) extracting free moisture from wet, dyed, tubular knitted, acrylic fabric to provide a fabric having a moisture content of less than about percent by weight;

(2) heating said fabric, preferably with hot air, at a temperature and for a time suicient to provide a fabric surface temperature of about ZOO-300 F. and a moisture content in the fabric of less than about 5 percent by weight;

(3) spreading and treating said fabric with steam to provide uniform moisture content on said fabric and a uniform Width throughout the fabric; and

(4) subjecting said fabric to treatment with radiant heat at a temperature and for a time suicient to provide a fabric surface temperature of about 20G-250 F.

The dyed, tubular knitted, acrylic fabric treated by the present process as defined above may then be processed into garments and knit wear by conventional means to provide end products having outstanding properties such as handle and appearance and substantially void of any dye streaks which normally pose a problem with acrylic knit Wear.

BRIEF DESCRIPTION OF THE DRAWINGSL FIG. 1 is a flow chart schematically showing a preferred embodiment of the instant process.

FIG. 2 is a process chart indicating, in greater particularity, process conditions for carrying out the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fabrics treated according to the present invention are dyed, tubular knitted fabrics comprised of at least 50 percent by Weight of acrylic fibers. The fabrics may consist wholly of acrylic fibers or they may consist of blends of acrylic fibers -with other fibers, such as cotton, wool, rayon, polyester, nylon, and the like. It is preferred that the fabric consist entirely of acrylic fibers. However, blends of acrylic fibers with up to 50 percent by Weight of other fibers are suitable for the purposes of this invention.

By the term acrylic fibers is meant fibers composed of copolymers, terpolymers, and blends thereof, all of which contain at least 80 percent by weight of polymerized or copolymerized acrylonitrile in the polymer molecule and corresponding up to about 20 percent by weight of other ethylenically unsaturated monomers copolymerizable therewith. The method of the present invention is applicable to tubular knitted fabric comprised of acrylic fibers which are formed from polymers containing at least 80 percent by weight of acrylonitrile in polymeric form. These include fibers formed from polyacrylonitrile, copolymers, and terpolymers containing at least 80 percent of acrylonitrile plus one or more mono-loetinic monomers copolymerizable therewith, and blended polymers and copolymers in which the blend composition contains at least 8O percent acrylonitrile. The blended polymers, for example, may comprise a major amount of a polymer of somewhat more than 80` percent acrylonitrile and a minor amount of another polymer or copolymer, the polymers being so proportioned that the blended polymer contains at least 80 percent acrylonitrile by weight.

The copolymers and terpolymers of at least 80 percent acrylonitrile may contain copolymerized therewith such other monooleiinic monomers as acrylic, haloacrylic, ana

methacrylic acids; esters such as methyl, butyl, octyl, methoxymethyl, and chloroethyl methacrylates and the corresponding esters of acrylic and haloacrylic acids; methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride, vinyl fluoride, vinylidene chloride, l-fluoro-lchloroethylene; vinyl carboxylates such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides such as N-vinylphthalrnide, and N-vinylsuccinimide, N-vinyllactams such as N-vinylcaprolactam and N-vinylbutyrolactam; aryl compounds such as styrene and vinyl naphthalene, and other compounds such as methyl vinyl ketone, methyl fumarate, methyl vinylsulfone, fumaronitrile, maleic anhydride, the vinyl pyridines such as 2-vinylpyridine, and 4-vinylpyridine, the vinylsubstituted alkyl pyridines, such as 4-ethyl-2-vinylpyridine, 5-ethyl-2-vinyl-pyridine, and 2-methyl-5-vinylpyridine; the isomeric vinylpyrazines, the various isomeric vinylquinolines, the vinylimidazoles and the vinylbenzoxazoles.

The acrylic fabrics subjected to the treatment of this invention are tubular knitted fabrics which have been subjected to any conventional dyeing processes using any conventional dyes. As an example, the acrylic fabric may be dyed using a conventional beck dyeing procedure wherein the fabric is dyed with a conventional basic or cationic dyestulf, such as Sevron Blue 2G (CI. Basic Blue 22), at atmospheric pressure and at a temperature of 212 F. The fabric to be treated by the process of this invention may also have been treated with one or more conventional ingredients used to enhance the physical characteristics of the fabric, such as emulsifying agents, wetting agents, softeners, durable press resins, and the like.

The wet, dyed, tubular knitted, acrylic fabric is then subjected to the critical steps of this invention as follows to provide a fabric having improved properties and processing when compared to conventional processing methods.

Free moisture is rst removed from the wet dyed fabric to provide a fabric having a moisture content of less than about 80 percent by Weight. This extraction may be conveniently carried out by any conventional method as by centrifuging, with pressure rolls, using vacuum slots, and the like. Preferably, this step will be carried out by centrifuging. The term free water as used herein refers to that water which is not held on the fabric in equilibrium at 100 percent relative humidity.

The fabric is then heated at a temperature and for a time suicient to provide a fabric surface temperature of about ZOO-250 F. and to provide less than about 5 percent by weight moisture content in the fabric. This drying step is preferably carried out by hot air drying in a conventional hot air oven equipped with means, such as contact thermocouples to measure the surface temperature of the fabric. Preferably, the hot air drying will be conducted at oven temperature of about 20G-260 F. for a period of about 40 to 60 seconds.

The fabric containing less than about 5 percent by weight moisture is then spread and subjected to a steam treatment. The steam treatment is used to provide a uniform moisture content on the dyed fabric and uniform width of the fabric and has been found to improve the bulk of the fabric. This spreading and steaming is done to provide a lubricating or plasticizing effect on the fabric to enable stretching of the fabric to full and uniform width prior to treatment with radiant heat. Normally, for the purposes of this invention, the fabric will be exposed to steam for about 1 to 3 seconds and it is preferred that dry steam be used.

From the steam treatment, the fabric is then subjected to a final heat treatment for a time and at a temperature sufiicient to raise the surface temperature of the fabric to a temperature of from about ZOO-250 F. Preferably, this heat treatment is carried out by means of radiant heating using infrared, microwave or dielectric energy. The particular method of providing the radiant heating depends upon economics, conditions, available equipment, and the like. Infrared energy is emitted over a range of wave lengths depending upon the temperature of the source. Lower temperatures emit longer wave lengths which are more penetrating. More energy can be given off by higher temperature sources but these tend to heat only the surfaces of the fabric, Microwave and dielectric energies are more penetrating but also are fore expensive. It has been found that the heating of the fabric in an infrared oven to a fabric temperature of about 220-230 F. is preferred. Preferably, the radiant heat treatment will be conducted at a temperature range of about 800-1200 F. for a period of about 15 to 20 Seconds. An Infra-Red Radplane oven, available from Infra-Red Systems, Inc. of Riverdale, NJ., is especially suitable for the purposes of this invention. Uniform heating is provided by top, bottom and edge heaters which are separately controlled. An open mesh conveyor belt allows the radiation to uniformly penetrate the bottom layer of the knits. The range will also be equipped with means, such as contact thermocouples, to measure the surface temperature of the fabric.

The dyed, tubular knitted acrylic fabrics treated according to the processing steps of this invention as described above may then be processed into a variety of end products, such as knit wear garments, by conventional means known to those skilled in the art. These knit goods will have outstanding characteristics, such as improved handle and being essentially free of dye streaks, when compared to identical knit wear processed by standard methods, such as by simply wet steaming the fabric followed by drying and finish calendering. In addition, the process of this invention is much more economical than this standard method in that knitted fabric may be processed at speeds of 25 yards per minute and greater using the process steps of this invention whereas maximum speeds of up to about 12 yards per minute can be achieved using the wet steaming, drying and finish calendering method.

Referring to FIG. 1 which represents a ow chart schematically showing a preferred embodiment of this invention, a typical run utilizing the processing steps of this invention, a typical run utilizing the processing steps of this invention will be explained. It is to be understood that the number, type and arrangement of rolls, apparatus, and the like may be varied for the purpose of carrying out the process of this invention.

Wet, dyed, tubular knitted, acrylic fabric 1 from a conventional beck dyeing bath is forwarded at speeds of about 27 yards per minute to a centrifuge extractor 2 where free moisture is extracted from the fabric to provide less than about percent by weight moisture on the fabric. From the centrifuge extractor, the fabric is passed through forwarding and spreader rolls 3, 4 and 5 and nip rolls 6 and 7 under a minimum amount of tension to a hot air oven 8 where the fabric is heated and dried at about ZOO-230 F. for a period of about 50 seconds to provide a fabric having a fabric surface temperature of about 20G-230 F. and having less than about 5 percent by weight moisture content. From the hot air oven, the fabric passes over forwarding roll 9 to an accumlator scray or pan 11 in which accumulation of fabric may occur as represented by 10. The fabric is then passed over an edge drive spreader 12 to provide and maintain a uniform width in the fabric and then over a streaming device 13 where the fabric is treated for about 2 seconds to provide uniform moisture content on the fabric. From the steaming device, the fabric passes over nip rolls 14 and 15 and under a minimum amount of tension forwarding roll 16 to an accumulator scray or pan '18 in which accumulation of fabric may occur as represented lby 17. The fabric from the accumulator scray is then passed over forwarding and yspreader roll 19 and through nip rolls 20 and 21 under a minimum amount of tension to au infrared oven 22 wherein the fabric is treated with radiant heat at a temperature range of about 800-1200 F. for a period of about 16-17 seconds to provide a fabric surface temperature of about 20G-250 F., preferably, about 220- 230 F. The fabric is then processed by conventional means, such as finish calendering, and the like, to provide fabrics having outstanding properties or characteristics as defined by this invention.

It is understood that changes and variations may be made in the present invention by one skilled in the art without departing from the spirit and scope thereof as dened in the appended claims.

What is claimed is:

1. A method for treating Wet, dyed, tubular Iknitted, acrylic fabric to improve the properties thereof which comprises:

(1) extracting free moisture from the dyed fabric to provide a moisture content in the fabric of less than about 80 percent by weight;

(2) drying the dyed fabric at a temperature of about 200 F. to 260 F. for a time sufficient to provide a fabric surface temperature of about 200 F. to 230 F. and a moisture content in the fabric of less than about percent by weight;

(3) spreading the dyed fabric and treating the dyed fabric with dry steam for a time sufficient to provide a uniform moisture content in the fabric and a uniform Width in the fabric;

(4) and then treating the dyed fabric with radiant heat at a temperature of about 800 F. to 1200 F. for a time sufficient to obtain a fabric surface temperature of about 220 F. to 230 F.

2. A method for treating Wet, dyed, tubular knitted, acrylic fabric to improve the handle of the fabric and to essentially eliminate dye streaks in the fabric which comprises:

(1) extracting free moisture from the dyed fabric by 6 centrifuging to provide a moisture content in the fabric of less than about 80 percent by Weight;

(2) drying the dyed fabric at a temperature of about 200 F. to 260 P. in a hot air oven for about 40 to seconds to provide a moisture content in the fabric of less than about 5 percent by Weight;

(3) spreading and treating the dyed fabric with steam for about 1 to 3 seconds to provide a uniform moisture content in the fabric and a uniform width in the fabric;

(4) and then subjecting the dyed fabric to infrared energy in an infrared oven at a temperature of about 880 F. to 1200 F. for about 15 to 20 seconds.

References Cited UNITED STATES PATENTS 3,484,949 12/ 1969 Aronoff.

FOREIGN PATENTS 631,857 11/ 1961 Canada. 750,529 6/ 1956 Great Britain. 862,301 3/1961 Great Britain.

OTHER REFERENCES Dupont Textile Fibers, NP-11, May 1960 Orlon Sayelle, page 14.

DONALD LEVY, Primary Examiner U.S. Cl. X.R. 

